Rotary device for mechanical rotational orientation of a well tractor

This invention relates to a method for the mechanical rotational orientation of a well tractor. More particularly, it relates to a method for the mechanical rotational orientation of a well tractor relative to a side pocket in a pipe. The well tractor, which is provided with wheels biased against the wall of the pipe, can, if a wheel rolls into a side pocket, be pulled back within the pipe, whereby a finger, which is connected to the well tractor and which bears, under bias, against the wall of the pipe, is brought to enter the side pocket, the finger following the edge portion of the side pocket during continued pulling back of the well tractor, thereby turning the well tractor about its longitudinal axis until the wheels of the well tractor are rotationally at the side of the side pocket. The invention also includes a device for practicing the method.

In connection with installation and maintenance work in a pipe, typically in a pipe associated with the recovery of petroleum, in which a so-called well tractor is used, it is well known that the well tractor may get stuck in so-called side pockets in the pipe.

Side pockets of this kind may be arranged to accommodate, for example, measuring equipment, valves or other auxiliary equipment facilitating the operation of the installation.

When one of the wheels of the well tractor which are biased against the pipe wall, rolls into a side pocket, it happens relatively often that the well tractor does not get any further into the pipe under its own power. Thus, it is often necessary to pull the well tractor back some distance by means of a connection, for example a cable, to the ground surface to get it loose again.

Subsequently another attempt must be made to run the well tractor past the side pocket. It is normal for this to be succeeded only after several attempts as prior art well tractors are not provided with means for steering clear of side pockets.

The invention has for its object to remedy or reduce at least one of the drawbacks of the prior art.

The object is achieved in accordance with the invention through the features specified in the description below and in the claims that follow.

A method in accordance with the invention for the mechanical rotational orientation of a well tractor relative to a side pocket in a pipe, the well tractor being provided with wheels that are biased against the wall of the pipe, is characterized by the well tractor being pulled rearwards within the pipe if a wheel rolls into a side pocket, whereby a finger which is connected to the well tractor and which is bearing, under bias, on the wall of the pipe, is brought to enter the side pocket, the finger following, during continued pulling back of the well tractor, the edge portion of the side pocket, thereby rotating the wheels of the well tractor about the longitudinal axis of the well tractor until the wheels of the well tractor are rotationally at the side of the side pocket.

The well tractor may then be run further into the pipe or it may be pulled back until the pulling force overcomes the force from a supporting spring whereby the finger slides out of the side pocket.

The finger, bearing under bias against the side wall and being movable into a side pocket, is typically pivotally connected to the well tractor. After the finger has pivoted into the side pocket, it will come to bear on the edge portion of the side pocket and be moved along this during the further movement of the well tractor in the pipe. The finger following the edge portion of the side pocket, the well tractor or more particularly the wheels of the well tractor are rotated about the longitudinal axis of the well tractor.

Side pockets of this kind are often oblong in the direction of the pipe, therefore providing a suitable lead-in of the finger towards a centred point which is centred, when the rotation has come to an end, between the wheels.

The finger is pivotal between a pivoted-in inactive position and a pivoted-out active position and biased against the wall of the pipe with a relatively small force.

Further, the finger is biased with a relatively great force in a mainly axial rearward direction. The support of the finger has been given a design which causes the finger, if this biasing force is overcome, to be moved into a pivoted-in inactive position.

To set the position of the finger relative to the wheels of the well tractor the finger is connected to a body rotation- ally adjustable relative to the longitudinal axis of the well tractor. Thereby, the angle of the finger relative to the wheels can be adjusted to achieve the intended effect.

The method and the rotary device according to the invention provide through their simple construction and operation a considerably improved rotational control of a well tractor, which could, to a substantial degree, make work of this kind more efficient.

In what follows, is described a non-limiting example of a preferred method and embodiment which are visualized in the accompanying drawings, in which:

Figure 1 shows a longitudinal section through a pipe and a rotary device;

Figure 2 shows a section Ia-Ia of figure 1 ;

Figure 3 shows a view Ib-Ib of figure 1;

Figure 4 shows the same as figure 1, but after the finger has been moved into the side pocket; and

Figure 5 shows the same as figure 4, but here the finger is on its way to be moved into its inactive pivoted-in position.

In the drawings the reference numeral 1 indicates a rotary device which is connected to the front portion of a well tractor 2. In front of the rotary device may be arranged a tool 5. An assembly of the well tractor 2 and the rotary device 1 is movable in a pipe 4.

In the pipe 4 is arranged a side pocket 6 illustrated in the drawings as a through opening in the wall of the pipe 4. The side pocket 6 is normally formed as a somewhat elongated opening preferably merging into a slit-shaped portion 8 at its part facing the ground surface.

A well tractor 2 includes wheels 10, see figure 2, which are distributed round the well tractor in a manner known per se.

At least some of the wheels 10 are driven and all are biased out against the internal wall of the pipe 4 to run, by means of friction, the well tractor 2 along the pipe 4. A well tractor 2 is known to a person skilled in the art and is therefore not described any further.

The rotary device 1 includes a first centre mandrel 12 and a second centre mandrel 14 connected to the first centre mandrel 12. The centre mandrels 12 and 14 are provided with a centre bore 16 extending therethrough and are formed with end flanges 18 complementarily fitting the well tractor 2.

A body 20 in the form of a finger housing rotatably surrounds the centre mandrels 12 and 14, the relative position of the finger housing 20 relative to the centre mandrels 12, 14 being fixable by means of locking screws 22.

The finger housing 20 is provided at least with a recess 24, in which a relatively elongated finger 26 is supported ^' in an oblong slot 28 about an axle 30. The axle 30, which is perpendicular to the longitudinal axis of the rotary device I ₁ is inside the recess 24. Thereby, the finger 26 is both ro- tatable and axially movable about the axle 30.

In this preferred embodiment the finger 26 is biased outwards against the pipe 4 by means of a blade spring 32. Other solutions, such as magnetic or electrically controlled actuators, not shown, may also be relevant for optionally moving the finger 26 towards the pipe 4.

When the finger 26 is in its pivoted-out active position, see figure 4, it bears on a cover 34.

A compression spring 36 is biasingIy disposed in a bore 38 in the cover 34, spanning between the recess 24 of the finger housing 20 and the end portion of the finger 26 extending in-

wards, at which the compression spring 36 is passed over a guide 40.

If the finger 26 is moved in the direction of the compression spring 36 along the slot 28, a chamfering 42 comes to bear on the cover 34, see figure 5, whereby the finger 26 is pivoted into its pivoted-in inactive position.

When the well tractor 2 together with the rotary device 1 is moved in along the pipe 4, the finger 26 can pivot into a side pocket 6 while passing the side pocket 6, see figure 4. However, due to a relatively small force from the blade spring 32, the finger 26 will pivot out of the side pocket 6 when passing it.

Should one of the wheels 10 of the well tractor roll into the side pocket 6 and the well tractor 2 thereby be prevented from being moved further in the pipe 4 , the well tractor 2 can under its own power or by means of some other force, for example via a cable, not shown, to the surface, be moved rearwards within the pipe 4.

The finger 26 will pivot into the side pocket 6 when the position of the finger coincides with the side pocket 6. During the further movement of the well tractor 2 in the pipe 4, the finger 26 will come to bear on the edge portion of the side pocket 6 and follow it in towards the slit-shaped portion 8. The finger 26 thereby rotates the well tractor 2 to a rotational position in which the wheels 10 do not correspond to the position of the side pocket 6.

If the well tractor 2 is moved further back, the finger 26 comes to bear on the end of the slit-shaped portion 8, see figure 5. When the force from the compression spring 36 is overcome, the finger 26 is moved along the slot 28 on the axle 30. The chamfering 42 comes to bear on the cover 34,

whereby the finger 26 is pivoted into its pivoted-in inactive position. Thereby, the well tractor 2 can freely be moved further back within the pipe 4. Alternatively, the well tractor 2 can be moved further into the pipe 4, the wheels 10 now being in a position in which they can pass the side pocket 6 without rolling into it.